"Its just that the se5a shelf,,, does that ever appear in a model cockpit?"
Yes. Please take the time to read my previous answer above.
Sandy
Before WNW Roden included the Instrument panel Lewis ammo storage in their 1/48th and 1/32nd SE5a kits. I don't know for sure but would guess also in their 1/72nd kit?
As for the Nieuport storage things are a bit more obscure. I think this was one of the first questions I asked when I joined the WW1 modeling "List" years ago. I remember a discussion on this Forum and IIRC the general opinion was on each side of the pilots seat . To Me that still seems to be an awkward location to retrieve them from during flight.
British Nieuport 17's and 23's used the Lewis gun only. That would mean that they would have no need of the ammo boxes or the belt and drum from the Vickers. I would find Myself asking if those items were removed and replaced with boxes or brackets for spare lewis drums.
In the end it seems No One has proof for any location on the Nieuports, ( at least those lacking outside boxes),so one could locate a drum anywhere it would not foul controls, piping, etc. and I doubt you could be proven wrong. JMHO,
RAGIII